Albrecht Unsöld
Encyclopedia
Albrecht Otto Johannes Unsöld (20 April 1905 – 23 September 1995) was a German astrophysicist known for his contributions to spectroscopic analysis of stellar atmospheres.
(Württemberg
), Germany
. After school attendance in Heidenheim, Unsöld studied physics
at the University of Tübingen and the University of Munich. At Munich, he studied under Arnold Sommerfeld
, and was granted his doctorate in 1927. As a Fellow of the Rockefeller Foundation, he was an assistant in Potsdam
and worked at the Mount Wilson Observatory
in Pasadena
, California
. He then completed his Habilitation
in Munich in 1929. In 1930, he was an assistant at the Institute of Theoretical Physics at the University of Hamburg
. In September 1932, Unsöld became Ordinarius Professor and Director of the Institute for Theoretical Physics (and Observatory) at the University of Kiel
– a position he held until his emeritus status was granted in 1973, after which he remained scientifically active for 15 years.
While a student at Munich, Unsöld was one of many of a long line of students who helped Sommerfeld explore and advance atomic theory
. Unsold's theorem states that the square of the total electron wavefunction for a filled or half-filled sub-shell is spherically symmetric. Thus, like atoms containing a half-filled or filled s orbital (l = 0), atoms of the second period with 3 or 6 p (l = 1) electrons are spherically shaped. Likewise, so are atoms of the third period in which there are 5 or 10 d (l = 2) electrons. Hence, spherical atoms are those of the 1st, 2nd, 7th, 12th, 15th and 18th columns of the periodic table.
At Kiel, Unsöld made an intensive study of the effects of abundances, radiation damping, Doppler shifts, electric fields, and collisions on the formation and shape of spectral lines in stellar atmospheres. His analysis of the B0 star Tau Scorpii
, obtained on his 1939 visit to Yerkes
and McDonald
Observatories, provided the first detailed analysis of a star other than the Sun
, and he was able to determine the physics and composition of the star’s atmosphere.
From 1947 to 1948, Unsöld was President of the Astronomische Gesellschaft.
Unsöld edited the Zeitschrift für Astrophysik until it was merged with other European journals into Astronomy and Astrophysics. He was also the author of many books, and his book Physik der Sternatmosphären mit besonderer Berücksichtigung der Sonne was a bible for quantitative stellar spectroscopy and related fields, with special emphasis on the Sun.
Career
Albrecht Unsöld was born in BolheimHerbrechtingen
Herbrechtingen is a town in the district of Heidenheim in Baden-Württemberg in southern Germany. It is situated on the river Brenz, 7 km south of Heidenheim, and 28 km northeast of Ulm.-References:...
(Württemberg
Württemberg
Württemberg , formerly known as Wirtemberg or Wurtemberg, is an area and a former state in southwestern Germany, including parts of the regions Swabia and Franconia....
), Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
. After school attendance in Heidenheim, Unsöld studied physics
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...
at the University of Tübingen and the University of Munich. At Munich, he studied under Arnold Sommerfeld
Arnold Sommerfeld
Arnold Johannes Wilhelm Sommerfeld was a German theoretical physicist who pioneered developments in atomic and quantum physics, and also educated and groomed a large number of students for the new era of theoretical physics...
, and was granted his doctorate in 1927. As a Fellow of the Rockefeller Foundation, he was an assistant in Potsdam
Potsdam
Potsdam is the capital city of the German federal state of Brandenburg and part of the Berlin/Brandenburg Metropolitan Region. It is situated on the River Havel, southwest of Berlin city centre....
and worked at the Mount Wilson Observatory
Mount Wilson Observatory
The Mount Wilson Observatory is an astronomical observatory in Los Angeles County, California, United States. The MWO is located on Mount Wilson, a 5,715 foot peak in the San Gabriel Mountains near Pasadena, northeast of Los Angeles...
in Pasadena
Pasadena, California
Pasadena is a city in Los Angeles County, California, United States. Although famous for hosting the annual Rose Bowl football game and Tournament of Roses Parade, Pasadena is the home to many scientific and cultural institutions, including the California Institute of Technology , the Jet...
, California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
. He then completed his Habilitation
Habilitation
Habilitation is the highest academic qualification a scholar can achieve by his or her own pursuit in several European and Asian countries. Earned after obtaining a research doctorate, such as a PhD, habilitation requires the candidate to write a professorial thesis based on independent...
in Munich in 1929. In 1930, he was an assistant at the Institute of Theoretical Physics at the University of Hamburg
University of Hamburg
The University of Hamburg is a university in Hamburg, Germany. It was founded on 28 March 1919 by Wilhelm Stern and others. It grew out of the previous Allgemeines Vorlesungswesen and the Kolonialinstitut as well as the Akademisches Gymnasium. There are around 38,000 students as of the start of...
. In September 1932, Unsöld became Ordinarius Professor and Director of the Institute for Theoretical Physics (and Observatory) at the University of Kiel
University of Kiel
The University of Kiel is a university in the city of Kiel, Germany. It was founded in 1665 as the Academia Holsatorum Chiloniensis by Christian Albert, Duke of Holstein-Gottorp and has approximately 23,000 students today...
– a position he held until his emeritus status was granted in 1973, after which he remained scientifically active for 15 years.
While a student at Munich, Unsöld was one of many of a long line of students who helped Sommerfeld explore and advance atomic theory
Atomic theory
In chemistry and physics, atomic theory is a theory of the nature of matter, which states that matter is composed of discrete units called atoms, as opposed to the obsolete notion that matter could be divided into any arbitrarily small quantity...
. Unsold's theorem states that the square of the total electron wavefunction for a filled or half-filled sub-shell is spherically symmetric. Thus, like atoms containing a half-filled or filled s orbital (l = 0), atoms of the second period with 3 or 6 p (l = 1) electrons are spherically shaped. Likewise, so are atoms of the third period in which there are 5 or 10 d (l = 2) electrons. Hence, spherical atoms are those of the 1st, 2nd, 7th, 12th, 15th and 18th columns of the periodic table.
At Kiel, Unsöld made an intensive study of the effects of abundances, radiation damping, Doppler shifts, electric fields, and collisions on the formation and shape of spectral lines in stellar atmospheres. His analysis of the B0 star Tau Scorpii
Tau Scorpii
Tau Scorpii is a star in the constellation Scorpius. Tau Scorpii also has the traditional name Alniyat or Al Niyat, which it shares with σ Scorpii. The name derives from the Arabic النياط an-niyāţ meaning "the arteries"....
, obtained on his 1939 visit to Yerkes
Yerkes Observatory
Yerkes Observatory is an astronomical observatory operated by the University of Chicago in Williams Bay, Wisconsin. The observatory, which calls itself "the birthplace of modern astrophysics," was founded in 1897 by George Ellery Hale and financed by Charles T. Yerkes...
and McDonald
McDonald Observatory
The McDonald Observatory is an astronomical observatory located near the unincorporated community of Fort Davis in Jeff Davis County, Texas, United States. The facility is located on Mount Fowlkes and Mount Locke in the Davis Mountains of West Texas...
Observatories, provided the first detailed analysis of a star other than the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
, and he was able to determine the physics and composition of the star’s atmosphere.
From 1947 to 1948, Unsöld was President of the Astronomische Gesellschaft.
Unsöld edited the Zeitschrift für Astrophysik until it was merged with other European journals into Astronomy and Astrophysics. He was also the author of many books, and his book Physik der Sternatmosphären mit besonderer Berücksichtigung der Sonne was a bible for quantitative stellar spectroscopy and related fields, with special emphasis on the Sun.
Honors
- 1956 – Bruce MedalBruce MedalThe Catherine Wolfe Bruce Gold Medal is awarded every year by the Astronomical Society of the Pacific for outstanding lifetime contributions to astronomy. It is named after Catherine Wolfe Bruce, an American patroness of astronomy, and was first awarded in 1898...
- 1957 – Gold Medal of the Royal Astronomical SocietyGold Medal of the Royal Astronomical Society-History:In the early years, more than one medal was often awarded in a year, but by 1833 only one medal was being awarded per year. This caused a problem when Neptune was discovered in 1846, because many felt an award should jointly be made to John Couch Adams and Urbain Le Verrier...
- The asteroidAsteroidAsteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...
2842 Unsöld is named in his honor.
Books
- Albrecht Unsöld Physik der Sternatmosphären mit besonderer Berücksichtigung der Sonne (Springer, 1955, 1968, and 1982)
- Albrecht Unsöld Max Planck (Hirt, 1958)
- Albrecht Unsöld Über die mittleren Zustandsgrössen und Spektren der Sternatmosphären in Abhängigkeit von ihrem Wasserstoff- und Heliumgehalt (Vandenhoeck & Ruprecht, 1958)
- Albrecht Unsöld Der neue Kosmos (Springer, 1967 and 1981)
- Albrecht Unsöld The New Cosmos (Longmans, 1969)
- Albrecht Unsöld Sterne und Menschen: Aufsätze u. Voträge (Springer, 1972)
- Albrecht Unsöld Evolution kosmischer, biologischer und geistiger Strukturen (Wissenschaftliche Verlagsgesellschaft, 1981 and 1983)
- Albrecht Unsöld und Bodo Baschek Der neue Kosmos. Einführung in die Astronomie und Astrophysik (Springer-Verlag GmbH, 1991, 2001, and 2004)
- Albrecht Unsöld und Bodo Baschek The New Cosmos (Heidelberg Science Library) (Springer-Verlag GmbH, 1991)
- Albrecht Unsöld, Bodo Baschek, W.D. Brewer (Translator) The New Cosmos: An Introduction to Astronomy and Astrophysics (Springer, 5th Edition, 2005) ISBN 978-3540678779
Selected literature
- Albrecht Unsöld Beiträge zur Quantenmechanik des Atoms, Ann. d. Phys. (4) 82 355-393 (1927). Received 22 December 1926, published in issue No. 3. of 8 February 1927. As cited in Mehra, Volume 5, Part 2, 2001, p. 959.